1. Field of the Invention
The present invention relates to a semiconductor memory, and more particularly to a dynamic memory having the function of executing a logical operation when it is read.
2. Description of Related Art
Heretofore, a semiconductor memory composed of dynamic memory cells includes at least one sense amplifier having a pair of inputs connected to a pair of bit lines. To each of bit lines, a plurality of memory cells and one dummy cell are connected, which are also connected to a corresponding number of different word lines and a dummy word line, respectively. In addition, there are provided one pair of input/output lines connected to the pair of bit lines through transfer gates.
With the above construction, when one memory cell connected to one bit line of the bit line pair is selected through the associated word line, a dummy cell connected to the other bit line is simultaneously selected through the associated dummy word line, and thereafter the sense amplifier is driven and the transfer gates are turned on, so that a pair of logical signals are read out to the input/output lines and at the same time, the read-out memory cell is refreshed.
However, the conventional semiconductor memory has no function of internally executing any logical operation between a plurality of items of information stored in the memory and of outputting the result of the logical operation. Therefore, once a required number of items of information are read externally from the memory, and a logical operation is executed on the read-out items of information in an exterior of the memory. Namely, in order to obtain the result of the logical operation there are required the read-out of the stored information and the actual execution of the operation for the read-out information. As a result, the logical operation speed is limited by the input/output speed of the memory, which allows only the read/write in the order of one bit to a few bits, and a high speed operation cannot be expected.